Method for producing polymeric ring-opening products

An n-protic Bronsted acid (C) having a degree of protolysis D of 0<D<n, wherein n is the maximum number of transferable protons where n=2, 3 or 4 and D is the calculated proton fraction of the organic, n-protic Bronsted acid (C),

• characterized in that
• the degree of protolysis D for diprotic acids where n=2 is 0.2 to 1.9, for triprotic acids where n=3 is 0.3 to 2.8 and for tetraprotic acids where n=4 is 0.4 to 3.7,
• wherein the organic, n-protic Bronsted acid (C) having the degree of protolysis 0<D<n is obtained by acid-base reactions with proton transfer by
• (β) addition of suitable amounts of at least one suitable Bronsted base (E) to the at least one organic, n-protic Bronsted acid, wherein the Bronsted base (E) contains at least one cation (F) selected from the group consisting of alkali metal-containing, alkaline earth metal-containing, metalloid-containing, transition metal-containing, lanthanoid metal-containing, aliphatic ammonium-containing and phosphonium-containing and sulfonium-containing cations
• or
• (χ) addition of suitable amounts of at least one suitable Bronsted acid (E′H) to the salt of the at least one organic, n-protic Bronsted acid, wherein the salts of the organic, n-protic Bronsted acid contains at least one cation (F′) selected from the group consisting of alkali metal-containing, alkaline earth metal-containing, metalloid-containing, transition metal-containing, lanthanoid metal-containing, aliphatic ammonium-containing and phosphonium-containing and sulfonium-containing cations, wherein the n-protic Bronsted acid (C) is at least one sulfonic acid and wherein the at least one sulfonic acid is selected from the group consisting of 1,5-naphthalenedisulfonic acid, 2,6-naphthalenedisulfonic acid and 1,3-benzenedisulfonic acid, preferably 1,5-naphthalenedisulfonic acid, 2,6-naphthalenedisulfonic acid, and very particularly preferably 2,6-naphthalenedisulfonic acid.